Lumber that has recently been cut contains a relatively large percentage of water and is referred to as green lumber. Prior to being used in applications that demand good grades of lumber, the green lumber must be dried. Drying removes a large amount of water from the lumber and significantly reduces the potential for the lumber to become warped or cracked. Although lumber may be dried in ambient air, kiln drying accelerates and provides increased control over the drying process.
Many manufacturing processes involve the use of water, if only for cooling purposes. Water that comes into contact with manufacturing processes is, with few exceptions, considered by environmental regulatory agencies to be “Process Water”. Process water is considered to be contaminated as a result of its contact with the manufacturing process. By regulation, process water, must not be allowed to drain freely away, thereby contaminating streams, watercourses, etc. The costs associated with conventional collection and treatment methods discourage compliance on the part of originators. More originators of process water exist than regulatory officials empowered to ensure compliance. Much process water is thus therefore allowed to escape and to detrimentally impact the environment.
Additionally, the water removed from the wood may eventually reach the point of saturating the space within the chamber with water vapor, at which point, the drying process would come to a halt, or at least be slowed considerably. By cooling the water vapor and condensing it into liquid water, the water vapor pressure in the chamber is kept below the saturation point, thereby continuing the evaporation of water from the wood, and avoiding the condensation of water on the wood. Many prior art kilns have mechanisms to remove excess condensation.
For example, in U.S. Pat. No. 4,343,095 to Rosen et al., water that accumulates on the bottom of the drying chamber from condensation of steam or from free water being forced out of the ends of the boards by internal pressure in the wood, is periodically ejected from the dryer.
In U.S. Pat. No. 5,595,000 to Goodwin, III, coils are used to control condensation. The air passing through the coil is cooled to well below the dew point which causes a condensation of moisture onto coil. The moisture condensed on coil is removed from the kiln by the condensate removal system.
U.S. Pat. No. 4,620,373 to Laskpwski et al. discloses a kiln that has evaporator hoses that condense the moisture that is removed from the wood into water, which is removed from the chamber into a storage tank by a pump.
U.S. Pat. No. 3,986,268 to Koppelman discloses a kiln that comprises a shroud or jacket to collect condensate. The condensate exits the tank through a drain at the bottom of the tank.
While care has been taken to control and/or remove condensation in and surrounding the kiln chamber, such measures do not address the problem of waste water or process water.
To overcome the above problems of properly dealing with and disposing of process water, waste water and/or condensation, the present inventors have proposed a method in which the volume of process water produced during a manufacturing process can be drastically reduced or eliminated.